This invention relates generally to improvements in water purification systems of the type having a reverse osmosis (RO) unit or the like for removing dissolved ionic material and other contaminants from an ordinary supply of tap water or the like. More particularly, this invention relates to an improved water purification system having a reverse osmosis unit adapted for providing a supply of relatively purified water over a significantly extended operating life, and wherein water waste during normal system operation is substantially eliminated.
Water purification systems in general are well-known in the art of the type having a reverse osmosis (RO) unit or membrane for converting an incoming supply of ordinary tap or feed water into relatively purified water for use in cooking, drinking, etc. In general terms, the reverse osmosis unit comprises a semi-permeable RO membrane through which a portion of the tap water supply is passed, such that the membrane acts essentially as a filter to remove dissolved metallic ions and the like as well as other contaminants and undesired particulate matter from the tap water. In normal operation, these impurities are removed from one portion of the water flow and concentrated in another portion of the water flow, commonly referred to as retentate or brine, which is normally discharged as waste to a drain. The thus-produced flow of relatively purified water is available for immediate dispensing for use, and/or for temporary storage within a suitable reservoir or vessel awaiting dispensing for use. A pure water dispense faucet mounted typically on or adjacent to a kitchen-type sink or the like is manually operable to dispense the produced purified water. While the specific construction and operation of such RO water purification systems may vary, such systems are exemplified by those shown and described in U.S. Pat. Nos. 4,585,554; 4,595,497; 4,657,674; and 5,045,197.
One disadvantage associated with reverse osmosis purification systems relates to the fact that retentate or brine outflow from the RO membrane is normally discarded as waste. In a typical RO system operating under standard domestic water supply pressures, the ratio of brine outflow to produced purified water outflow can be on the order of about 4:1. Accordingly, the discarded brine flow is sometimes perceived as a relatively substantial waste of water which can be significant in areas wherein the water supply is limited. As a result, many residential and commercial water customers have favored use of bottled water as a purified water source, despite the costs and inconveniences associated with delivery, storage and changeover of large (typically 5 gallon) water bottles with respect to a bottled water cooler.
Another disadvantage associated with reverse osmosis systems relates to the typically limited service life of the RO membrane and other pre-filter and post-filter elements typically associated therewith. More specifically, many RO systems use a pre-filter element typically including a carbon-based filtration media for removing some contaminants from a tap water inflow at a location upstream from the RO membrane. One important function of this pre-filter element is to remove contaminants that would otherwise shorten the operating service life of the RO membrane. A downstream-located post-filter element is also commonly provided for additional water filtration and purification before dispensing. This array of pre- and post-filter elements, in combination with the RO membrane, is often provided in the form of individual cartridges designed for facilitated disassembly from and re-assembly with a unitary-type manifold. See, for example, U.S. Pat. No. 5,045,197. Despite the fact that cartridge replacement may be required only once each year, and despite efforts to make cartridge changeover an intuitively simple process, many customers are reluctant to handle this task. Instead, replacement of the various RO system cartridges has largely remained the responsibility of a water service company, thereby entailing regular and relatively costly service calls to each customer's residence or place of business. The requirement for regular service calls dramatically increases the overall operating cost of the RO system, thereby reducing or eliminating apparent advantages relative to conventional bottled water coolers and related bottle delivery systems.
There exists, therefore, a significant need for further improvements in and to reverse osmosis water purification systems, wherein water waste is substantially eliminated, and further wherein the service life of a reverse osmosis (RO) membrane is significantly extended for at least a period of several years without requiring attention by service personnel. The present invention fulfills these needs and provided further related advantages.